state of practice approaches in geomorphology ......state of practice approaches in geomorphology,...

Presentation to Department of Energy

Natural Phenomena Hazards Meeting

October 21-22, 2014

State of Practice Approaches in Geomorphology, Geochronology

and Probabilistic Analyses for Addressing Fault Capability at

Nuclear Facilities

Click to edit Master title style

2

Overview

• Case history on application of state of practice site characterization investigations for assessing the suitability of two sites for a proposed second nuclear power plant (NPP) at Krško, Slovenia • Site Characterization investigations to evaluate capability of

faults within 5 km of planned NPP sites (2) • PFDHA conducted to assist utility in making informed

decision on suitability of proposed NPP sites with respect to the probability of surface fault displacement

Click to edit Master title style

3

Overview

• Site characterization investigations follow IAEA SSG-9 guidance include • Tectonic geomorphic analyses related to landscape

evolution • Geochronology based on multiple methods for constraints on

faulting • High resolution seismic (refraction & reflection) surveys to

identify extent of faulting in site vicinity • Probabilistic evaluation of fault displacement hazard to

support • Utility in assessing nuclear safety • Regulatory decision-making following IAEA SSG-9

• Focus of investigations on Libna Fault that is mapped in close proximity to proposed eastern NPP site

Click to edit Master title style

4

BACKGROUND

• Krško, Slovenia is located in southeastern Slovenia in an area defined by a triple junction between the Alps, Dinarides, and the Pannonian Basin • Region is within the transition zone between the Sava Folds and

the southeastern extension of the Mid-Hungarian Shear Zone • Region of moderate seismicity

• Paleoseismic investigations conducted prior to 2012 demonstrated the Libna Fault to be: • Capable based on age • within 1-2 km of the existing proposed sites for Krško NPP 2

Click to edit Master title style

5

Background (Cont’d.)

• Utility and expert reviewer questioned the interpretation of the Libna Fault’s capability by previous investigators based on: • Questionable optical stimulated luminescense (OSL) ages

(possible at saturation limits – i.e. the maximum age capacity)

• Inferred projections of the Libna and other faults • Judgments made based on limited, and potentially unreliable

data

Click to edit Master title style

6

Tectonic Framework of Adriatic Microplate transition zone at northern extent of Mid Hungarian Shear Zone

Click to edit Master title style

7

Sites Libna Flt

Approximate Lineament Map surrounding the Krško Basin

Click to edit Master title style

8

Trench Excavated Across Libna Fault

From GeoZS 2013

Trench excavated in high-density, karst landscape -- brings into question the mode of recent displacement

Trench wall faces south

Click to edit Master title style

9

Trench map of notable Karstic dissolution features

Click to edit Master title style

10

LiDAR DEM

Deep-seated landslide provides local analog for ‘exaggeration’ of the Libna Feature – site located ~12 km from Libna Trench Extensive karst is common to region (note the sinkholes) Note difference between 1m LiDAR DEM and conventional 5m resolution DEM

1m DEM 5m DEM

Click to edit Master title style

11

Lineament map Based on DEM derivatives

Click to edit Master title style

12

Libna Hill Morphology

Signatures of: • Faulting? • Landsliding? • Karst?

Click to edit Master title style

13

3D oblique images

Click to edit Master title style

14

Enhanced LiDAR DEM showing location of trench relative to karst and landsliding Apparent continuity in SE corner is a fluvial scarp – proven with additional trenching Indicating

location of trench Fluvial scarp

Click to edit Master title style

15

High Resolution Seismic Survey

• Seismic survey designed to explore extension of the Libna fault in the Krško basin

• Used high resolution refraction & reflection approach designed for identifying near surface features

• Develop hybrid, diving wave refraction tomography for additional near-surface characterization

• Faults were identified but no faulting observed in the upper Miocene marls • Marl underlie young valley fill (10-120m) • Dip direction of faults identified in HRS survey tend to have dip

direction opposite that of the Libna fault • Suggests a lack of fault continuity

Click to edit Master title style

16

Plan View Showing Possible Faults

Click to edit Master title style

17

Krsko Basin Sediments

OSL sediment “depositional” ages • CRN elevation

(322 m) ~1.8 Ma • Libna Trench

(140 ka) (315-320 m) elevation

• OSL elevations

(150-215) m

Click to edit Master title style

18

Conceptual capacity of OSL in the Krsko Basin

All other age dates

CRN date

OSL date

Click to edit Master title style

19

Quaternary Aggradation and Incision Scenarios

To accept the Libna Trench OSL age, there are two scenarios necessary: • Catastrophic aggradation of Sava River: greater than 100m/

1,000 years

• Catastrophic incision of Sava River: greater than 100m/1,000 years

*There is no evidence for any catastrohic events that occurred in the region that could have led to either of these scenarios

• Moderate incision of Sava River (0.09m/1,000 years) this is consistent with incision rates of the southern Alps

• Suggests provides a more representative age than the Libna Trench OSL age.

Long term = 0.09m ka-1

Click to edit Master title style

20

Findings of Geomorphic, Geophysical and Geochronology Investigations Investigations

• Libna Hill and surrounding area is dominated by karst and landsliding

• Apparent offset of the Globoko Fm. May be greatly exaggerated by karst and landsliding

• CRN analyses suggests age of Globoko Fm. Is approximately same as published interpretations

• Use of OSL may be limited to dating sediments around 200Ka in the region (not unusual for OSL limitations)

• Libna fault, if displacement of Globoko is tectonic has an age of less than 1.7 Ma

• Libna fault may be discontinuous within the Miocene bedrock with a maximum length of 1.5 to 4.5 km

Click to edit Master title style

21

PFDHA

• Methodology: Petersen et al. (2011) • Extension of “earthquake” approach developed by

Youngs et al. (2003) for the Yucca Mountain Project

• Treats on-fault and off-fault displacement • Uses Petersen et al. fault displacement data base • Accounts for uncertainty related to fault mapped location

accuracy & fault complexity

Click to edit Master title style

22

Key PFDHA Inputs

• Probability of activity • Fault length • Fault location • Slip rate • Maximum magnitude • Hazard calculation cell size • Fault location uncertainty (mapping accuracy

and fault complexity)

Click to edit Master title style

23

Fault Model

45.85

45.95

46.05

15.4 15.5 15.5 15.6 15.6 15.7 15.7 15.8 15.8

Latit

ude

(Deg

N)

Longitude (Deg E)

Libna Gabrnica

Gorica

Sromljica

Stara Vas

Mocnik 1

Mocnik 2

Orlica N

Orlica S

Click to edit Master title style

24

Krško PFDHA Results

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.001 0.01 0.1 1 10

Mea

n A

nnua

l Fre

quen

cy o

f Exc

eeda

nce

Displacement (m)

East SiteWest Site

Total Hazard

Click to edit Master title style

25

Fault Source Contribution-East Site

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.001 0.01 0.1 1 10

Mea

n A

nnua

l Fre

quen

cy o

f Exc

eeda

nce

Displacement (m)

Total hazard Artice_Extended_East Artice_Extended_West Artice_LongArtice_Short Gabrnica_A Gabrnica_B Gorica_AGorica_B Hrastnik Libna_A Libna_BLibna_C Mocnik_1 Mocnik_2a Mocnik_2bOrlica_North Orlica_South Sromljica_A Sromljica_BStara_Vas_A Stara_Vas_B

Orlica South

Stara Vas B

Libna A & B

East Site

Source: RIZZO (2013a, Figure 14)

Click to edit Master title style

26

PFDHA Findings

• Petersen et al. methodology is appropriate for PFDHA application in the geologic setting of Krško

• The probability of exceeding surface displacement values of about 5 cm or greater at the Krško East and West Sites is very low: about 10-8 or less

• Libna fault does not pose a suitability issue for either sites

• This finding also applies to the existing Krško 1 NPP Site

Click to edit Master title style

27

Conclusions

• Tectonic geomorphic and landscape evolution methods should be applied, that rely on multiple age dating methods and high resolution topography. Combined, these methods allow for a broader understanding of the processes that shape the landscape, including faulting, karstic dissolution, landsliding and fluvial erosion.

• PFDHA has had limited application in assessing suitability of existing and proposed NPP sites; however, its application has been beneficial to aiding decision makers in assessing site suitability.

Click to edit Master title style

28

Contact Information

• K. Michael Cline – Michael.Cline@rizzoassoc.com • M. Logan Cline –

Mlogan.Cline@rizzoassoc.com • Richard Quittmeyer –

Richard.Quittmeyer@rizzoassoc.com